Defense Express explains.In light of Washington's officially confirmed decision to suspend the transfer of ammunition and missiles to Ukraine, with the risk of turning this temporary decision into a permanent one, it is important to understand what anti-aircraft missile systems Ukraine's air defense may be left with.If stockpiles of surface-to-air missiles aren’t replenished — which is exactly what’s at stake right now — then any air defense system, whether it’s a Patriot or a Stinger MANPADS, becomes useless and can be shelved. Without missiles, it’s powerless. This is precisely the situation that forced Ukraine to modernize parts of its Soviet-era systems, as missiles for them became scarce. That eventually led to the development and deployment of the so-called Franken-Buks - Buk-M1 systems adapted to fire AIM-7 missiles.It may therefore make sense to focus on foreign air defense systems that use non-American munitions.At the lowest level are MANPADS: the Polish Piorun, French Mistral, Swedish RBS-70, and British Martlet (LLM). In this category, the only American system is the Stinger. There may also still be stockpiles of missiles for the Soviet-era Igla and Strela systems.One step up, among the short-range SAMs with a range of up to 10 km: the British Stormer for Martlet and Starstreak missiles, German unnamed systems for Thales' FZ275 LGR missiles (analogous to APKWS), which were designated as Raketenwerfer 70mm auf Pick-up truck (70mm missile launcher on a pick-up truck). Among the American solutions are the Avenger missile system with Stinger missiles, as well as the Vampire for APKWS.As for the Ukrainian solutions, in addition to the Soviet Strela-10, this category includes the original and transferred to the P-73 Osa systems, as well as independent solutions based on this missile. Moreover, the British Gravehawk in a containerized form factor was created for the P-73.Among the short-range SAMs that can hit targets at ranges up to 20 km are the German IRIS-T SLS and the British Raven with ASRAAM missiles on the SupaCat chassis. Also in this category are Spain's Spada air defense systems, which were discussed back in 2022 but never materialized.Among Soviet solutions, the S-125 and Tor may still be in service, if they still have missiles. But the US is formally absent from this category. But the aforementioned Franken-Buks with AIM-7 are likely to have a range of 20 km, at least the officially known range of the naval version of RIM-7 is 19 km.Among medium-range air defense systems, the situation becomes more difficult. Of the foreign systems that do not use American missiles, only the German IRIS-T SLM remains. The Norwegian NASAMS, which has been supplied in greater numbers than the German systems, uses AIM-9 and AIM-120 missiles. Missile supplies for the MIM-23 HAWK also depend on the United States.As for Soviet-era air defense systems like the Buk and the S-300P - which during the Soviet period were supplied with 5V55 missiles with a range of up to 75 km - the key issue again is where to get Soviet-made missiles for these systems.When it comes to long-range air defense systems with missile defense capabilities, it's important to focus not on the system names but on the numbers and actual capabilities. For example, only two batteries of the French-Italian SAMP/T have been delivered, compared to around ten Patriot batteries. At the same time, shortages of missiles for the SAMP/T are also known.Thus, Ukraine’s air defense is heavily dependent on the supply of American missiles: Stinger, APKWS, AIM-7, HAWK, GEM-T, and MSE, as well as AIM-9 and AIM-120. The latter are also used by F-16s, which are necessary for effectively engaging aerial targets. At the same time, the segment of air defense involving anti-aircraft artillery and machine guns is only indirectly dependent on U.S. supplies. There is also less reliance on U.S. missiles for short- and very short-range systems.